The present application is based on Japanese Patent Application No. 2000-384831, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to improvement of a small-sized motor used for lens drive of a camera.
2. Description of Related Art
FIG. 2 is a sectional view of a small-sized motor with a lead screw, which is used for purposes of lens drive of a camera and the like. As shown in FIG. 2, in this motor, a metal frame 3 having a C-shaped section is fixed to one axial end of a stator 2 opposed to a rotor 1. Further, a bearing 4a is fitted into the other axial end of the stator 2, and one end of a rotary shaft 11 inserted and fixed into the rotor 1 is rotatably supported by this bearing 4a. 
In this rotary shaft 11, its other end side protrudes from the stator 2, and its leading end is rotatably supported by a bearing 4b fitted into the metal frame 3. The portion of the rotary shaft 11 protruding from the stator 2, that is, the portion arranged in the metal frame 3 having the C-shaped section functions as an output portion 11a, at which a lead screw is formed. By rotation of the rotary shaft 11, this lead screw feeds axially an operation member (not shown) for operating a lens, whereby the lens is moved.
Such a conventional small-sized motor with a lead screw for driving a lens, since the metal frame 3 is attached to one end of the stator 2 as described above, has problems that an attaching method of the motor to another member is limited and that space-saving is difficult. Further, since the bearings 4a and 4b receiving each end of the rotary shaft 11 are supported respectively by the stator 2 and the metal frame 3 which are different members, shaft accuracy is not easy to obtain. Further, since the number of parts is large, assembly efficiency is bad, which makes it more difficult to obtain the shaft accuracy.
The inventors thought that the metal frame 3 was removed from one end of the stator 2 in consideration of the space saving and the assembly efficiency. In this case, it is necessary to fit a metal bearing for rotate-supporting a portion in the middle of the output shaft 11 to one end of the stator 2, that is, onto the attaching surface of the metal frame 3 in the above-mentioned example. However, regarding fitting of this metal bearing, the workability is bad. In case that the stator 2 and the metal bearing are integrally manufactured by insert molding in consideration of the work performance, a molding die is so complicated so that a problem of high cost is caused.
An object of the invention, in view of the above-mentioned problems, is to provide, in a small-sized motor used for lens drive, the motor which is easy to attach to another member and gives space saving. Further, another object of the invention is to provide a motor in which the number of parts is reduced thereby to improve assembly efficiency and shaft accuracy is good.
In order to achieve such the objects, a motor of the invention comprises a rotor; a rotary shaft inserted and fixed into the rotor; a stator core constituting a stator opposed to the rotor; an output side bearing provided on an output side of the rotary shaft, and supporting a portion near an output portion of the rotary shaft; and an opposite side bearing holding portion for holding an opposite side bearing supporting an opposite side to the output side of the rotary shaft; wherein the stator core, the output side bearing and the opposite side bearing holding portion are integrally formed by insert molding, and the output side bearing and the opposite side bearing holding portion are made of resin.
According to the invention, since the output side bearing and the opposite output side bearing holding portion, which were conventionally constituted by a different member from the stator, are formed integrally with the stator cores by insert molding, the number of parts can be reduced and position accuracy can be improved.
Further, the invention is characterized in that in the above-mentioned motor, a lead screw is formed at the output portion and a rotation of the lead screw directly affects an operated member.
Further, the invention is characterized in that in the above-mentioned motor, the opposite side bearing, which is urged to the output side and comprises an axially movable slide bearing, is arranged in a hole of the opposite output side bearing holding portion, and that an end of the rotary shaft is supported by this opposite output side bearing. Therefore, the rotary shaft can be exactly rotated axially in the more stable position, so that rotational position accuracy can be heightened.
Further, the invention is characterized in that in the above-mentioned motor, a hole having an inner diameter larger than an outer diameter of the rotor is formed in the opposite side bearing holding portion.
Further, in order to achieve the objects, a motor of the invention comprises a rotor, and a stator opposed to the rotor and constituted by stator cores, wherein the stator cores, and an output side bearing that rotates and supports a side, near an output portion for operating an operated member, of a rotary shaft inserted and fixed into the rotor are formed integrally by insert molding; the output side bearing is made of a resin; a lead screw is formed from the output portion of the rotary shaft to a portion thereof opposed to an inner surface of the output side bearing; and lubricant is filled in an opposed gap between the lead screw and the output side bearing.
According to the invention, since the output side bearing, which was conventionally constituted by a different member from the stator, is formed integrally with the stator cores by insert molding, the number of parts can be reduced and the position accuracy can be improved. Further, according to the invention, the lead screw is formed up to the portion of the rotary shaft opposed to the inner surface of the output side bearing, and the lubricant is filled in its portion. Therefore, though the metal frame that has been used in the related art is removed and the portion in the middle of the rotary shaft is held by the bearing, the rotating operation of the lead screw is smooth and run-out of the shaft is not produced.